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checksum.h

/* 
 * Licensed under the GPL
 */

#ifndef __UM_SYSDEP_CHECKSUM_H
#define __UM_SYSDEP_CHECKSUM_H

#include "linux/in6.h"
#include "linux/string.h"

/*
 * computes the checksum of a memory block at buff, length len,
 * and adds in "sum" (32-bit)
 *
 * returns a 32-bit number suitable for feeding into itself
 * or csum_tcpudp_magic
 *
 * this function must be called with even lengths, except
 * for the last fragment, which may be odd
 *
 * it's best to have buff aligned on a 32-bit boundary
 */
__wsum csum_partial(const void *buff, int len, __wsum sum);

/*
 *    Note: when you get a NULL pointer exception here this means someone
 *    passed in an incorrect kernel address to one of these functions.
 *
 *    If you use these functions directly please don't forget the
 *    access_ok().
 */

static __inline__
__wsum csum_partial_copy_nocheck(const void *src, void *dst,
                               int len, __wsum sum)
{
      memcpy(dst, src, len);
      return csum_partial(dst, len, sum);
}

/*
 * the same as csum_partial, but copies from src while it
 * checksums, and handles user-space pointer exceptions correctly, when needed.
 *
 * here even more important to align src and dst on a 32-bit (or even
 * better 64-bit) boundary
 */

static __inline__
__wsum csum_partial_copy_from_user(const void __user *src, void *dst,
                               int len, __wsum sum, int *err_ptr)
{
      if (copy_from_user(dst, src, len)) {
            *err_ptr = -EFAULT;
            return (__force __wsum)-1;
      }

      return csum_partial(dst, len, sum);
}

/*
 *    This is a version of ip_compute_csum() optimized for IP headers,
 *    which always checksum on 4 octet boundaries.
 *
 *    By Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
 *    Arnt Gulbrandsen.
 */
static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
{
      unsigned int sum;

      __asm__ __volatile__(
          "movl (%1), %0      ;\n"
          "subl $4, %2  ;\n"
          "jbe 2f       ;\n"
          "addl 4(%1), %0     ;\n"
          "adcl 8(%1), %0     ;\n"
          "adcl 12(%1), %0    ;\n"
"1:       adcl 16(%1), %0     ;\n"
          "lea 4(%1), %1      ;\n"
          "decl %2            ;\n"
          "jne 1b       ;\n"
          "adcl $0, %0  ;\n"
          "movl %0, %2  ;\n"
          "shrl $16, %0 ;\n"
          "addw %w2, %w0      ;\n"
          "adcl $0, %0  ;\n"
          "notl %0            ;\n"
"2:                     ;\n"
      /* Since the input registers which are loaded with iph and ipl
         are modified, we must also specify them as outputs, or gcc
         will assume they contain their original values. */
      : "=r" (sum), "=r" (iph), "=r" (ihl)
      : "1" (iph), "2" (ihl)
      : "memory");
      return (__force __sum16)sum;
}

/*
 *    Fold a partial checksum
 */

static inline __sum16 csum_fold(__wsum sum)
{
      __asm__(
            "addl %1, %0            ;\n"
            "adcl $0xffff, %0 ;\n"
            : "=r" (sum)
            : "r" ((__force u32)sum << 16),
              "0" ((__force u32)sum & 0xffff0000)
      );
      return (__force __sum16)(~(__force u32)sum >> 16);
}

static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
                                       unsigned short len,
                                       unsigned short proto,
                                       __wsum sum)
{
    __asm__(
      "addl %1, %0      ;\n"
      "adcl %2, %0      ;\n"
      "adcl %3, %0      ;\n"
      "adcl $0, %0      ;\n"
      : "=r" (sum)
      : "g" (daddr), "g"(saddr), "g"((len + proto) << 8), "0"(sum));
    return sum;
}

/*
 * computes the checksum of the TCP/UDP pseudo-header
 * returns a 16-bit checksum, already complemented
 */
static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
                                       unsigned short len,
                                       unsigned short proto,
                                       __wsum sum)
{
      return csum_fold(csum_tcpudp_nofold(saddr,daddr,len,proto,sum));
}

/*
 * this routine is used for miscellaneous IP-like checksums, mainly
 * in icmp.c
 */

static inline __sum16 ip_compute_csum(const void *buff, int len)
{
    return csum_fold (csum_partial(buff, len, 0));
}

#define _HAVE_ARCH_IPV6_CSUM
static __inline__ __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
                                const struct in6_addr *daddr,
                                __u32 len, unsigned short proto,
                                __wsum sum)
{
      __asm__(
            "addl 0(%1), %0         ;\n"
            "adcl 4(%1), %0         ;\n"
            "adcl 8(%1), %0         ;\n"
            "adcl 12(%1), %0  ;\n"
            "adcl 0(%2), %0         ;\n"
            "adcl 4(%2), %0         ;\n"
            "adcl 8(%2), %0         ;\n"
            "adcl 12(%2), %0  ;\n"
            "adcl %3, %0            ;\n"
            "adcl %4, %0            ;\n"
            "adcl $0, %0            ;\n"
            : "=&r" (sum)
            : "r" (saddr), "r" (daddr),
              "r"(htonl(len)), "r"(htonl(proto)), "0"(sum));

      return csum_fold(sum);
}

/*
 *    Copy and checksum to user
 */
#define HAVE_CSUM_COPY_USER
static __inline__ __wsum csum_and_copy_to_user(const void *src,
                                         void __user *dst,
                                         int len, __wsum sum, int *err_ptr)
{
      if (access_ok(VERIFY_WRITE, dst, len)) {
            if (copy_to_user(dst, src, len)) {
                  *err_ptr = -EFAULT;
                  return (__force __wsum)-1;
            }

            return csum_partial(src, len, sum);
      }

      if (len)
            *err_ptr = -EFAULT;

      return (__force __wsum)-1; /* invalid checksum */
}

#endif

/*
 * Overrides for Emacs so that we follow Linus's tabbing style.
 * Emacs will notice this stuff at the end of the file and automatically
 * adjust the settings for this buffer only.  This must remain at the end
 * of the file.
 * ---------------------------------------------------------------------------
 * Local variables:
 * c-file-style: "linux"
 * End:
 */

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